As examples of the conventional linear motion guide device of this type, for example, the devices disclosed in Japanese Patent Laid-Open Publication No. SHO 55-46045 and No. SHO 55-46046 are well known. That is, each of the devices comprises a track rail and a movable block having an L-shape in section, and the movable block further comprises a horizontal portion opposing to an upper surface of the track rail and a suspending portion opposing to one side surface of the track rail.
Two rows of rolling balls were disposed to be rollable between two opposing surfaces of the upper surface of the track rail and the horizontal portion of the movable block, and between two opposing surfaces of the one side surface of the track rail and the suspending portion of the movable block, respectively.
The conventional linear motion guide device of this type has a following contact-angle structure. Namely, in the two rows of rolling balls provided on the upper surface of the track rail, a contact angle line constituted by a line connecting the two contact points of the rolling balls to the ball rolling grooves corresponding to the respective ball rows is set to extend toward the track rail and is formed so as to incline toward a side of the suspending portion with respect to a vertical line passing a center of the rolling ball in a case of the ball row positioned close to the suspending portion side, while the other contact angle line in a case of a ball row positioned at the other side of the suspending portion is set to extend toward the track rail and is formed so as to incline toward an opposing side of the suspending portion.
In contrast, in the pair of rolling balls provided on the side surface of the track rail, a contact angle line constituted by a line connecting the two contact points of the rolling balls to the ball rolling grooves corresponding to the respective ball rows is set to extend toward the track rail and is formed so as to incline toward a side of the horizontal portion with respect to a horizontal line passing a center of the rolling ball in a case of the ball row positioned close to a side of the horizontal portion, while the other contact angle line in a case of a ball row positioned at the other side of the horizontal portion is set to extend toward the track rail and is formed so as to incline toward an opposing side of the horizontal portion.
Due to an employment of such contact-angle structure, a load-bearing capacity against loads to be applied from various directions including vertical and horizontal directions can be enhanced. In particular, it becomes possible to increase a supporting rigidity against a moment in a direction for rotating the movable block around the track rail.
In the prior art technics described above, however, since the supporting rigidity against the moment in the direction for rotating the movable block around the track rail is high, there were posed following problems. Namely, when the movable block in a state having a working error in attaching surfaces thereof is fixed to a table and then the track rail is fixed to a fixed bed, a misalignment is caused between the track rail and the movable block and an excessive force is applied to the track rail and the movable block, thus resulting in increasing of sliding resistance and promoting early wear of the ball rolling grooves and rolling balls per se. Such misalignment will be avoided by increasing working precision of the respective members of the device. However, the working precision has a limit itself and involves a cost increasing.
The present invention is achieved for solving the aforementioned problems and an object of the present invention is to provide a linear motion guide device and a table guide device using the linear motion guide device which has an automatic controllability and enables to realize a supporting structure having a high rigidity.